ML18096B281

LER 93-002-00:on 920116,manual Reactor Trip Initiated When 12 Sgfp Tripped Due to Turbine Trip FW Isolation Signal. Caused by Equipment Failure.Faulty Turbine Bypass Sys Components replaced.W/930211 Ltr

ML18096B281
Person / Time
Site:	Salem
Issue date:	02/11/1993
From:	Pollack M, Vondra C Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-002, LER-93-2, NUDOCS 9302220468
Download: ML18096B281 (5)

Text

e OPS~G Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station February 11, 1993 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Dear sir:

SALEM GENERATING STATION LICENSE NO. DPR-70 DOCKET NO. 50-272 UNIT NO. 1 LICENSEE EVENT REPORT 93-002-00 This Licensee Event Report is being submitted pursuant to the requirements of the Code of Federal Regulations lOCFR 50.73(a) (2) (iv). This report is required to be issued within thirty (30) days of event discovery.

Sincerely yours, fY13t?oLc7?

~Vondra General Manager -

Salem Operations MJP:pc Distribution 190119 The Energy People 9302220468 930211 PDR ADOCK 05000272 S PDR

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I re9, U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3150-0104 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD LICENSEE EVENT REPORT (LERI COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P-530), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 2050:1.

FACILITY NAME 11) DOCKET NUMBER (21 PAGE 131 Salem Generating Station - Unit 1 O I5 I o I O I O I 'l I 7 1? I 1 OF n It.

TITLE 141 Manual Reactor Trip due to Trouble with the Turbine Bypass System.

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EVENT DATE (5) LER NUMBER (61 R EPDRT DATE 171 OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR /}: SE~~~~~~AL Jt ~EX.:~~ MONTH DAY YEAR FACILITY NAMES DOCKET NUMBER(S) 9 3 913 - ol o 12 - d o o12 i I1 9 I3 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE R~QUIREMENTS OF 10 CFR §: (Ch*ck one or more of the following) (111 t-~~~~~

MODE (9)

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NAME

- 60.73(1)(21{ii) 60.73(11(21 (iii)

LICENSEE CONTACT FOR THIS LER (121 60,73(1)(2)(viiil(B) 60.73(1)(2Hxl TELEPHONE NUMBER AREA CODE M. J. Pollack - LER Coordinator 61 0 19 3 13 19 I - 12 D 12 12 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFAC* MANUFAC*

TUR ER TUR ER B SID PI CIOI W1l I 210 N I I I I I I I I I I I I I I I I I I I I I SUPPLEMENTAL REPORT EXPECTED (141 MONTH DAY YEAR EXPECTED n ~NO SUBMISSION DATE 1151 YES (If yes, comploto EXPECTED SUBMISSION DATE)

I I I ABSTRACT (Limit to 1400 spaces, i.e., approximately fiftt111n sing/a-space typt1writtt1n linas} 116)

On 1/16/93, during shutdown to Mode 3 (Hot Standby} for maintenance, a manual reactor trip was initiated when 12 Steam Generator Feedwater Pump (SGFP} tripped (11 SGFP was cleared and tagged} due to a turbine trip/feedwater isolation signal (from a 13 Steam Generator (S/G)

High-High Level signal). Prior to the turbine trip, Turbine Bypass system control was being transferred from Tave" to "Steam Pressure".

During this evolution, Turbine Bypass Valves went full open causing a S/G "swell". 13 S/G swelled to the high-high level alarm setpoint resulting in the turbine trip/feedwater isolation signal, an Engineered Safety Feature (ESF}. Per design, the 20 valves which provide steam from the S/Gs to the Turbine-Generator isolated and the operating SGFP tripped.

Following this, the Turbine Bypass System valves were closed and a manual Reactor trip was initiated. Plant response was as expected following the reactor trip including the degree of Reactor Coolant System cooldown (as has occurred after prior plant trips). Per procedure, a Main steamline Isolation (an ESF) was initiated stopping the cooldown. The plant was stabilized in Mode 3. The root cause of this event is equipment failure. The Turbine Bypass Pressure Controller and the associated servo potentiometer module of the Turbine Bypass Control System failed causing the controlling station setpoint to go from -1040 psi to 196 psi in -5 seconds. This caused the Turbine Bypass Valves to fully open. The faulty Turbine Bypass System components were replaced. The Unit was returned to service 1/24 .

N RC Farm 366 (6-891

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 93-002-00 2 of 4 PLANT AND SYSTEM IDENTIFICATION:

Westinghouse - Pressurized Water Reactor Energy Industry Identification System (EIIS) codes are identified in the text as {xx}

IDENTIFICATION OF OCCURRENCE:

Manual Reactor Trip due to trouble with the Turbine Bypass System Event Date: 1/16/93 Report Date: 2/11/93 This report was initiated by Incident Report No.93-047.

CONDITIONS PRIOR TO OCCURRENCE:

Mode 1 Reactor Power 16% - Unit Load 130 MWe DESCRIPTION OF OCCURRENCE:

On January 16, 1993, at 0952 hours0.011 days <br />0.264 hours <br />0.00157 weeks <br />3.62236e-4 months <br />, during shutdown to Mode 3 (Hot Standby) for planned maintenance, a manual reactor trip was initiated when 12 Steam Generator Feedwater Pump (SGFP) tripped due to a turbine trip/feedwater isolation signal. This signal initiated from a 13 Steam Generator (S/G) High-High Level signal. At the time of the event, 11 SGFP was cleared and tagged in support of maintenance.

Prior to the turbine trip, Operations personnel were transferring Turbine Bypass System control from "Tav 11 to "Steam Pressure" per Integrated Operating Procedure, IOP-5, nMinimum Load to Hot Standby",

and Operations Procedure OP-III-2.3.4, "Steam Dump System Normal Operation". During this evolution, Turbine Bypass Valves ll-13TB10 and 11-13TB20 unexpectedly went full open causing a S/G "swell". 13 S/G swelled to the high-high level alarm setpoint resulting in the turbine trip/feedwater isolation signal.

Turbine trip/feedwater isolation is an Engineered Safety Feature (ESF). Per design, the twenty (20) valves which provide steam from the S/Gs to the Turbine-Generator isolated and the operating SGFP tripped. Following this, the Turbine Bypass System valves were closed (from the Control Room by turning the Turbine Bypass Controls to "OFF") and a manual Reactor trip was initiated per Alarm Response Procedure, Sl.OP-AR.ZZ-0006(Q).

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 93-002-00 3 of 4 DESCRIPTION OF OCCURRENCE: (cont'd)

Plant response was as expected following the reactor trip including the degree of Reactor Coolant system {AB} cooldown (as has occurred after prior plant trips). In accordance with Emergency Operating Procedure EOP-TRIP-2, a Main Steamline Isolation (an ESF} was initiated stopping the cooldown. The plant was stabilized in Mode 3.

APPARENT CAUSE OF OCCURRENCE:

The root cause of this event is equipment failure. The Turbine Bypass Pressure Controller (PC-507) and the associated servo potentiometer module of the Turbine Bypass Control System failed causing the controlling station setpoint to go from -1040 psi to 196 psi in approximately five (5) seconds. This caused the Turbine Bypass Valves to fully open. Troubleshooting duplicated the sequence of events.

A review of Turbine Bypass System work orders did not identify signal component problems similar to those experienced in this event.

ANALYSIS OF OCCURRENCE:

In conjunction with the Rod Control System, the Turbine Bypass System provides Tav control below 15% reactor power. The system provides for a variabie artificial steam load. The system is not required for either safe plant operation or safe shutdown. It is designed to pass 40% of rated steam flow.

The manual reactor trip was anticipatory and is a standard practice to limit undue demand on the automatic protection system. Had the operators not manually tripped the reactor; the plant would have tripped on S/G Low-Low level. All systems functioned as designed and the Reactor was placed in a stable condition.

The Reactor Protection System (RPS} {JC} functioned as designed and the heat sink was maintained during this event. Since the RPS is designed for the thermal and hydraulic effects of four-hundred (400}

full power reactor trips, this low power reactor trip resulted in a thermal transient well within the design limits of the system. This event therefore involved no undue risk to the health or safety of the public. However, due to the Turbine Trip/Feedwater Isolation actuation, RPS system actuation, and the initiation of Main Steamline Isolation, the circumstances surrounding these events are reportable in accordance with Code of Federal Regulations lOCFR 50.73(a) (2) (iv).

The reduction in Tavg' requiring main steamline isolation, has been experienced during o~her reactor trips (e.g., Unit 2 LER 311/92-009-00). Engineering has investigated Tavg reduction (during trips) and design modifications are being assessed.

J Salem Generating Station DOCKET NUMBER

• LICENSEE EVENT REPORT (LER) TEXT CONTINUATION LER NUMBER PAGE Unit 1 5000272 93-002-00 4 of 4 CORRECTIVE ACTION:

The faulty Turbine Bypass System components were replaced, calibrated and tested satisfactorily. The Unit was returned to service January 24, 1993, after completion of the planned maintenance activities.

EQUIPMENT FAILURES:

Component: Turbine Bypass Pressure Controller Manufacturer: Westinghouse Model: 124 (Serial #H0-114)

.~CJ{7~~.rV

~~l Manager - .

Salem Operations BWL:pc SORC Mtg.93-014